Year	Percent
1960	23.70819
1961	23.64538
1962	23.80502
1963	24.40456
1964	23.75973
1965	24.26699
1966	24.24955
1967	24.43064
1968	26.12839
1969	26.79086
1970	26.35888
1971	27.0529
1972	26.21745
1973	27.19912
1974	27.63
1975	26.94469
1976	25.91656
1977	25.38149
1978	24.91106
1979	24.18173
1980	22.03158
1981	21.80806
1982	20.42305
1983	19.52398
1984	21.6853
1985	21.59447
1986	21.02938
1987	21.07944
1988	20.11045
1989	19.86511
1990	19.15984
1991	18.33846
1992	19.10732
1993	18.90795
1994	19.26004
1995	18.92515
1996	18.01365
1997	16.4491
1998	14.74667
1999	15.19436
2000	13.94109
2001	13.30281
2002	13.44841
2003	13.15095
2004	13.9844
2005	13.51755
2006	13.36125
2007	13.60651
2008	14.51607
2009	14.54021
2010	13.74887
2011	14.09574
2012	13.09581
2013	12.47343
2014	12.27168
2015	10.9965
2016	10.20513
2017	10.18295
2018	9.65014
2019	8.82032
2020	10.18531
2021	10.06917
2022	9.54935